A virtual machine (VM) is a software implementation of a computer that executes programs like a physical machine. The VM supports an operating system (commonly referred to as a guest operating system) and application programs, which run on the VM transparently, as though it was an actual physical machine. Multiple virtual machines may share the same underlying physical machine resources. A software layer known as a virtual machine monitor (VMM, also referred to as a hypervisor) provides virtualization support to the VMs by mediating between the VM software and the underlying physical hardware.